Track section clearing apparatus for railway signaling systems



Sept. 3, 1940.

H. G. BLOSSER TRACK SECTION CLEARING APPARATUS FOR RAILWAY SIGNALING SYSTEMS Filed Dec. 29, 1938 Fig. 2.

INVENTOR Herman loafer.

HIS ATTORN EY Patented Sept. 3, 1940 S'i-TES TRACK SECTION CLEARING APPARATUS FQR RAELWAY SIGNALING SYSTEIVES Application December 29, 1938, Serial No. 248,272

15 Claims.

My invention relates to track section clearing apparatus for railway signaling systems and it has special reference to the use of such apparatus in systems which. employ coded track circuit energy to control wayside and/or cab signals.

Generally stated the object of my invention is to eliminate the need for line wires in detecting the movement of trains out of track sections which extend r arwardly from highway crossing or other cuts in signal block lengths of the coded system track.

A more specific object is to provide non-linewire track section clearing apparatus which is operable under the special track. circuit conditions that are produced by the passage of trains through the subdivided signal blocks and which is unresponsive to foreign energy in the track circuits of those blocks.

Another object is to minimize the danger of improper operation of the track section clearing apparatus upon accidental failure of the signaling system track relay to respond to coded track circuit energy.

In practicing my invention, I attain the above and other objects and advantages by transmitting code step pulses of auxiliary energy forwardly through the rails of the section which extends rearwardly from the cut to a code following detector relay which is installed at the location of the out. In receiving and responding to this auxiliary energy the detector relay causes an associated slow release relay to maintain the highway crossing signals or other out section apparatus inactive under all vacant conditions 0 of the rear section (including times when the section ahead. of the cut may still be occupied). When a train comes into the rear section and cuts ofi transmission of the auxiliary energy, the detector relay becomes inactive and then allows the slow release relay to drop out for the purpose of bringing the cut section apparatus into operation. This operation continues until the departing train clears the exit end of the rear section at which time the detector relay once more receives auxi iary energy and restores the cut section apparatus to its normally inactive conclitlon.

I soall describe several forms of approach conrol apparatus embodying my invention and shall 0 then point out e novel features thereof in claims. These ll rative embodiments are disclosed in the accompanying drawing in which:

Fig. l is a diagrammaticrepresentation of a signal block length of railway track which is equipped with one preferred form of my improved track section clearing apparatus;

. Fig. 2 is a partial representation of the entrance end facilities of Fig. 1 arranged in a somewhat modified manner and r Fig. 3 is a diagrammatic showing of a modified form of out section location facilities which are usable with the track section clearing scheme of Fig. 1.

In the several views of the drawing like reference characters designate corresponding parts. Referring first to Fig. l, the improved track section clearing apparatus of my invention is there disclose-d in association with a coded track circuit system of automatic block signaling for a railway track l-2 over which it will be assumed that trafiic moves in the single direction indicated by the arrow, or from left to right in the diagram. The protected stretch of this track is divided into the customary successive sections by insulated rail joints and the rails of each section form a part of a track circuit to which coded signal control energy is supplied in customary manner.

In this view of Fig. 1, reference characters D and E respectively designate the entrance and the exit ends of a full signal block length of the track 5-42 and character Dc designates the location of a out which subdivides this block into a rear track section D-Da and an adjoining forward track section DaE. This particular cut is occasioned by a highway -l which intersects the track and with which a crossing signal XS is associated to warn the users of that highway when railway tramc approaches the intersection over the rearwardly extending section DDa.

Positioned at the entrance of each of the signal block lengths of the represented track is the usual wayside signal S together with the customary control apparatus therefor. This apparatus includes a code following tracl: relay TR which receives recurring pulses of operating energy from the rails of the associated section of track. That energy, in turn, comes from a track battery or other direct current source TB which is in stalled at thev section exit and there intermittently connected with the section rails by a coding contact 5.

As shown at the exit end location E of the main signal block DE, this coding contact forms a part of a coding device CR. which, under the control of the customary facilities (not shown) of the coded signaling system is continuously operated at one or another of the usual plurality of distinctive code rates. Selection among these rates (which in a typical three indication system may consist of 75 and 180 energy pulses per minute) is made in accordance with advance traffic conditions by decoding apparatus functioning in customary manner.

As partially represented at location D in Fig. 1, this decoding apparatus may make use of a pair of decoding relays DRlS and DRiBii receiving energy from the usual decoding transformer DT under the control of the code following track relay TR. Transformer DT is provided with a direct current exciting circuit which is pole changed in conventional manner by a contact 9 of the track relay; the transformer secondary supplies energy to the first decoding relay DRlS over a circuit which includes a second or current rectifying contact H of the track relay arranged in the manner disclosed and claimed in a copending application Serial No. 210,744 filed May 28, 1938, by Frank H. Nicholson et al.; and the second decoding relay DR: is energized from the primary circuit of the decoding relay through a resonant unit DUI 88.

By virtue of the frequency selective characteristics of unit DUNN], this second decoding relay DREBEJ is responsive only to energizing voltages from transformer DT which have the particular frequency that results when the track relay TR receives operating energy of the pulse per minute code. The first decoding relay DRlS, however, is non-selective and is arranged to pick up when the track relay responds to operating energy of either the '35 or the I88 trackway code.

In addition to selecting the coding of the energy which is supplied to the rails of the track section to the rear (through facilities which include a code repeating relay of the type shown at CR at location E), the decoding relays DR'l5 and DRlBE perform the further function of selectively completing a lighting circuit for one or another of the lamps (G, Y and R in the typical three indication system above referred to) of the wayside signal S at the same location. In the arrangement shown, this signal lamp control is effected by contacts 6 and E.

An automatic block signaling system of the representative coded track circuit type herein disclosed operates without the aid of line wires and to clarify the description of my new track section clearing apparatus which follows presently, the manner in which this operation takes place will now be reviewed. To facilitate this review, it will first be assumed that the insulated joints 3 now shown at the cut location Do are absent from the main signal block DE and that the rails of that block are electrically continuous from the exit end E thereof to the entrance end D thereof.

As long as the protected stretch of track of which block DE forms a part remains vacant, the exit end facilities at location E supply the rails of the block with energy of the E89 coding, the track relay TR at the entrance end of the block responds to this energy in the usual code following manner, the associated decoding relays DR'ifi and DRlSil are both picked up, the clear lamp G of the controlled wayside signal S is supplied with lighting current, and coding facilities (not shown at location D) supply the rails of the track section to the rear with energy of the I86 or clear code.

In the event that a train travelling in the di rection indicated by the arrow enters the signal block DE, the usual shunting action of its wheels and axles continuously deenergizes the track relay TR at location D, both of the decoding relays DR'l5 and DRlBO become released, the stop lamp R of the controlled signal S is supplied with lighting current and the above referred to coding facilities (not shown) supply the rails of the track section to the rear with energy of the T5 or caution coding.

As the rear of the departing train clears the exit location E, the facilities at that location (shown as including track battery TB and coding device CR) supply energy of this '75 pulse per minute code rate to the rearwardly extending rails, those rails transmit this energy to the entrance end track relay TR, that relay responds and picks up the associated decoding relay DR-l5 only, the caution lamp Y of the signal S is now lighted, and the rails of the section to the rear receive energy of the 180 pulse per minute code.

When the rear of the departing train clears the exit end of the signal block of which location E marks the entrance, the coding relay CR. at that location operates at the higher rate to supply energy of the till] code to the rails of track block DE. In responding to that energy relay TR at the entrance location D causes both of the decoding relays DRTS and DRISO to pick up and thereby restores the apparatus at that location to the normal or clear track stretch condition.

Referring now to the cut section apparatus which I have represented at location Da in Fig. i. this includes a code following track relay TRc operated by energy received from the rails of forward section Da-E and a track battery TB which is connected in energy supplying relation with the rails of the rear section DDa each time that contact 5 of relay 'IRa is picked up. In this manner each pulse of coded energy received from the forward section rails is repeated into the rails of the rear section and the presence of the cut section joints 3 at location Da thus does not alter the just explained operation of the coded signaling system.

For applications in which train carried cab sig nals (not shown) also are to be controlled, the representative coded signaling facilities may still further comprise means at the exit end of each track circuit for additionally supplying the rails thereof with coded alternating current energy. 0

In the form shown at each of locations Da and E in Fig. 1, these means include a track transformer TT having a secondary winding which is serially included in the circuit over which the track battery TB supplies energy to the track rails each time that coding contact 5 is in the uppermost position. At proper times the primary winding of this transformer is energized from a suitable alternating current source designated by the terminals 5 and C.

In order that the highway crossing protective signals XS at the cut location Dc may be rendered active only upon the approach of a train over the rear track section DDa, the apparatus installed at the cut section location Da is supplemented by an approach relay AR which is arranged to maintain the crossing signal inactive at all times except when the track section DDa becomes occupied. This control of the signal is effected through the medium of a contact 53 which when released completes for the signal XS an operating circuit which may be traced from the positive terminal of a suitable supply source through back contact l3, conductor l4 and the operating mechanism of the signal back to the negative terminal of the supply source.

Also governed by the approach relay AR at the cut section location is the supply of coded alternating current energy for cab signal control to the rails of the rear track section D-Da. This function is controlled by a second contact E5 of the approach relay. When that contact is in the released position, the primary of track transformer TT at the out section is energized from the alternating current source B--C over a circuit which extends from terminal B through back contact l5, conductor E6, the primary of trans former TT and conductor i'l back to terminal C.

When, however, the contacts of relay AR are picked up, the transformer is disconnected from the energizing source and the primary winding thereof is then by-passed by way of a circuit which extends from the right terminal of the Winding through conductor l6, front contact E5 of relay AR and conductor it back to the left ter minal of the winding. The purpose of this bypassing is to reduce the impedance to the flow of direct current from the track battery TB which the secondary of transformer TT prevents under deenergized conditions of the transformer primary.

It will be apparent that either of the two signaling functions just named (control of the crossing signal XS and the supply of alternating current energy to the track circuit) may be controlled individually by the approach relay AR and as the description proceeds it will be evident, moreover, that signaling functions other than or in addition to those just named may likewise be governed by the same relay. Typically, such further functions may consist in operating detector locking track circuits (not shown) as well as in clearing out detector track sections generally.

When applied to a coded signaling system of the conventional character just considered, the improved track section clearing apparatus herein disclosed renders the relay AR at the cut section location responsive to the approach of a train over the rearwardly extending section D-Da and does this, moreover, without the use of line wires.

As illustratively shown in association with the rearwardly extending track section DDa of Fig. 1, this improved apparatus comprises: (1) Entrance end facilities which supply the section rails with recurring pulses of auxiliary energy under all vacant conditions of the section and in such manner that those pulses coincide with the oif periods of the coded signal control energy which at times is received over the rails from the section exit and (2) Exit end facilities which receive these auxiliary pulses from the rails and energize the approach relay AR in step with them, whereby to maintain that relay picked up under all vacant conditions of the section and to cause it to release only when the transmission of the auxiliary energy is cut off by the presence of rolling stock the section.

In the form shown at location D in Fig. 1, my improved entrance end facilities comprise a bettery or other source of auxiliary energy AB, an

impulse relay IR which transfers the connection of the track rails i and 2 from the track relay TR to battery AB during each ofi period of the received signal control code, means including contacts l9 and 2d of relays TR and DRI5 for supplying the impulse relay IR with pick-up energy at proper times, and means for causing the impulse relay to continue to supply recurring pulses of auxiliary energy to the rails when no coded signal control energy is received therefrom.

This impulse relay m is a slow releasing device and is provided with a contact 2i which occupies the lowermost position (shown in full lines) under conditions of relay deenergization and then serves to connect the operating winding of the track relay TR directly across the track rails l and 2. When, however, relay IR becomes energized, it moves contact 2! upwardly into the picked up position (shown dotted) and thereby disconnects the track rails from the relay TR. This action is the same as that disclosed and claimed by: (1) a first copending application Serial No. 222,014 filed July 29, 1938, by Herman G. Blosser and (2) a second copending application Serial No. 225,371 filed August 17, 1938, also by Herman G. Blosser.

Connectd'd in parallel circuit relation with back contact 25 of the represented relay IR is a front contact 22 of relay TR which assures that once the track relay TR becomes picked up the connection of its operating winding with the rails will be continuously maintained until the end of the pulse of coded signal control energy which initiated the relay pick-up.

Pick-up current for the impulse relay IR is derived from the battery AB over a circuit which includes the before referred to contacts l9 and 2i) of relays TR and DRIE. As long as the track relay TR is receiving and responding to coded signal control energy from the section rails, the decoding relay DR15 holds contact 20 continuously in the picked up position shown and contact H! of relay TR then completes the impulse relay energizing circuit during each on period of the received code. This picks up the relay IR shortly after the beginning of each of the on periods.

At the beginning of each off period which follows, contact W of relay TR interrupts the energizing circuit for relay IR, but, being slow releasing, that relay IR stays picked up until just before the beginning of the succeeding on code period. When thus picked up, contact. 2| of relay IR sets up a circuit by way of which contact E9 of the track relay TR connects the auxiliary battery AB across the track rails l and 2 during the first portion of each of the referred to oil periods. In this manner each release of the track relay TR causes the impulse relay IR momentarily to transfer the track rail connection from the winding of relay TR to the output circuit of battery AB.

In the event that no coded energy is received by the track relay TR from the rails, it continuously releases and causes decoding relay DRIS also to release its contacts. Under these conditions, the pick-up circuit for the impulse relay IR is so modified as to cause that relay to continue recurrently to pick up and release and thereby intermittently connect the auxiliary battery AB with the track rails for the purpose of continuing the supply of recurring pulses of auxiliary energy thereto under those conditions of the section in which no coded signal control energy is received from the exit end thereof.

The impulse relay energizing circuit now includes released. contact B9 of relay TR, a back contact 23 of relay IR and released contact 29 of relay BRIE. By virtue of the inclusion of this back contact 23 in the relay energizing circuit, the impulse relay IR is, under the conditions stated, caused to pick up and release at a rate which is determined by the release period of that relay. Preferably this release time is chosen to be slightly less than the Off period lengths of the 585 signal control code and for purposes of explanation it may be assumed to have the value of one-tenth second.

Accordingly, as long as both the relays TR and DR remain continuously released, impulse relay IR will recurrently pick up and release at a rate which approximates ten times per second. Each time that the relay picks up, contact 2! thereof connects battery A5 with the rails over a circuit which includes back contact H) of relay TR and contact 23 interrupts the pick-up circuit for the relay IR. At the expiration of its release period, the contacts return to their lowermost positions and contact 23 reestablishes the circuit over which the winding of relay IR receives pick-up energy from the battery AB. In this manner the rails of the track section continue to be supplied with recurring pulses of auxiliary energy when no coded signal control energy is received therefrom by the track relay TR.

In the form shown at location Do in Fig. 1, the cooperating exit end facilities comprise a detector relay KR which responds (in the manner disclosed and claimed by a copending application Serial No. 221,317, filed July 2'5, 1938, by Edward U. Thomas) to pulses of auxiliary energy received over the rails l and 2 from battery AB, a circuit controlled by a contact 25 of that relay for energizing the approach relay AR from a local source designated by the terminals plus and minus, and means for making the relay AR sufficiently slow releasing to bridge the intervals between recurrent responses of the detector relay.

This detector relay KR is of the code following type and the operating winding thereof is connected in energy receiving relation with the track rails l and 2 during each off period of the signal control code which contact 5 of device TRa produces. From an inspection of Fig. 1 it will be seen that this connection is interrupted during the on code periods when contact 5 is in the uppermost position; furthermore, it will be observed that since the named connection is completed when contact 5 occupies its lowermost or off period on it is continuously established when the relay TRa fails to receive coded signal control energy from the rails of the forward section Da-E, as when those rails are by-passed by rolling stock in the section.

The slow release approach relay AR may be energized in step with the responses of the detector relay KR in any suitable manner. As shown in Fig. 1, the contact 25 of the detector relay is directly included in the circuit of the operating winding for the approach relay. For delaying the release of this relay AR and thereby enabling it to remain continuously picked up as long as its winding receives code step pulses of energizing current, use may, of course, be made of any suitable means, such as a snubbing impedance (not shown) or internal design. expedients incorporated in the relay. Because of their well-known character, the drawing makes no attempt to represent any such means.

The manner in which the complete track section clearing system of Fig. 1 operates will now be considered. During this consideration it will first be assumed that the signal block length of track DE is vacant and then that a train moves through the section in the direction indicated by the arrow.

Under the first assumed vacant conditions of the track section, the coding device CR at the exit end of the signal block operates in the usual manner to supply the rails of the forward section DaE with coded signal control energy and the rails of both the forward and the rear sections DaE and D-Da act in the usual manner to transmit energy from one end of the section to the other as long as these rails are not by-passed by rolling stock. Each time, under such conditions, that contact 5 of the coding device CR is in the uppermost position the track battery TB at location E picks up the track relay TRa at location Da over a circuit which may be traced from the positive terminal of the battery through an impedance 2?, front contact 5 of device CR, conductor 28, track rail i, conductor 29, the winding of relay TRa, conductor 30, track rail 2, conductor 3| and the primary of transformer TT back to the negative terminal of battery TB.

In responding to each pulse of this received pick-up energy, contact 5 of relay TRa connects the track battery TB at the cut section location with the rails of the rear section D-Da and thereby picks up the track relay TR at the entrance of that section. The now effective pickup circuit for relay TR at location D extends from the positive terminal of the battery TB at location Da through impedance 2?, front contact 5 of relay 'IRa, conductor 33, track rail l, conductor 3 the winding of relay TR, conductor 35, back contact 2| of relay IR, conductor 36, truck rail 22, conductors 3i and 38 and the secondary of transformer TT back to the negative terminal of battery 'IB.

In picking up in response to the energy which relay TR receives over the circuit above traced, contact 22 of that relay by-passes back contact 2! of relay IR and thereby makes available between conductors 35 and 36 another path which extends from conductor 35 through conductor 39, front contact 22 of relay TR and conductor 40 back to conductor 35. In this manner each time that the cut section battery TB is connected with the rails of the rear section it picks up the rear section track relay TR over back contact 2! of release impulse relay IR and establishes at front contact 22 a path which continues the winding of relay TR connected with the rear section rails for the full duration of the "on code period. This connection, moreover, is not disturbed even though the impulse relay IR becomes picked up during that period.

Preliminary to describing how the impulse relay IR responds under various conditions of operation of the signaling system, it may again be observed that when the signal block D-E is vacant the track relay TR at the entrance end thereof picks up and releases in step with the on and the off periods of the signal control code which the exit end device CR produces and that under such unoccupied conditions of both of the track sections D-Da and Da-E the entrance end decoding transformer DT (controlled by contacts 9 and. H of relay TR) supplies the decoding relay DR'IS with energy which holds the contacts of that relay continuously picked up.

At the beginning of each on period of the received signal control code to which the track relay TR responds under the stated vacant conditions of the signal block, contact !9 of relay TR picks up the impulse relay IR over a circuit which may be traced from the positive terminal of the auxiliary battery AB through conductor 42, front contact IQ of relay TR, front contact 20 of relay DR'JS, conductor 43, the winding of relay IR and conductors Ml and 45 back to the negative terminal of battery AB. In now picking up, contact 2| of relay IR sets up the circuit over which the battery AB supplies the track rails l and 2 of the rear section with auxiliary energy. This circuit, however, remains interrupted until contact l9 of relay TR releases at the end of the on code period.

In picking up, contact 2i of relay IR also interrupts the original connection of the track relay TR with the rails. However, before that connection is broken, contact 22 of relay TR establishes, as has already been pointed out, a parallel or stick connection over which the energy received from battery TB at the cut section location continues to flow through the track relay Winding until the end of the on code period.

Each time that the coding contact of the cut section device 'IRa occupies the lowermost or off code period position, it not only connects the winding of the detector relay KR across the rails of the rear section but also releases the track relay TR at the entrance end of that section. Contact 22 of the track relay now breaks the above mentioned stick path and thereby disconnects the track rails l and 2 from the winding of relay TR. At the same time, this contact it of relay TR completes the circuit over which the rear section rails receive auxiliary energy from the battery AB. Once completed, this circuit is maintained intact until one or the other of the contacts 99 and 2i changes its position.

In the case of contact I9 of relay TR, this shift occurs at the beginning of the succeeding on code period, while in the case of contact 2! of relay IR this shift or release occurs at the expiration of the release delay period of relay IR. In practice, this period will preferably be chosen to be just slightly less than the length of the shortest off period of the several codes which the signaling system uses. In the case of the three indication system previously mentioned as employing codes of '75 and 180 energy pulses per minute, this shortest off period occurs in the I88 code the cycle length of which is 0.33 second and the ofi period length of which is about 0.16 second.

Because of the joint action of relays TR and IR just explained as taking place during each off period of the received signal control code, the auxiliary battery AB becomes effective during each of these 011" periods to pick up the detector relay KR at the out section location over a circuit which may betraced from the positive terminal of battery AB'through conductor 32, back contact E9 of relay TR, conductor 5?, an impedance 48, front contact 2d of relay IR, conductor 38, track rail 2, conductor 31', the winding of relay KR, conductor A9, back contact 5 of coding device 'IRa, conductor 33, track rail l and conductors 34 and 55 back to the negative terminal of the battery AB.

Under the influence of each of these pulses of auxiliary energy which is received from the trackway, code following detector relay KR picks up and contact 25 thereof completes for the approach relay AR a local energizing circuit which may be traced from the positive supply terminal through front contact 25, conductor 5i and the winding of relay AR back to the negative supply terminal.

As a result of these recurring pulses of local energization, the slow release approach relay AR now holds its contacts I3 and i5 continuously picked up and thereby maintains the crossing protective signal XS inactive and the track transformer TT at location Da deenergized as long as the rear track section DDa remains vacant.

It will now be assumed that a train traveling in the direction indicated by the arrow passes through the stretch of track which is embraced by the signal block [3-3. As enters the rear section D--Da, the shunting action of its wheels and axles reduces to a very low value the potential difference between the rails l and El and thus deprives both of the relays TR and KR of pick-up energy. Relay KR now remains continuously released and the supply of local energization to the approach relay AR is discontinued. In consequence, that relay now completes at contacts l3 and I5 the energizing circuits for the crossing signal KS and the track transformer TT. As a result, the named signal now comes into operation and warns the users of highway i that a train is approaching the intersection over the track section of track D -Da.

At the same time, the transformer TT sup-' plies the rails of the named section with a pulse of alternating current energy from source B-C each time that the contact 5 of device occupies its uppermost position. As has been mentioned, this energy is suitable for the control of train carried cab signals and the circuit over which it is supplied may be traced from the right terminal of the secondary winding of transformer TT through the track battery TB, impedance 21?, front contact 5 of coding device TRa, conductor 33, rail i, the wheels and axles (not shown) of the train, rail 2 and conductors 3i and 38 back to the left terminal of the track transformer secondary.

Meanwhile, the apparatus at the entrance end I) of the rear section responds to the continuously released conditions of relays TR and DRlii and supplies recurring pulses of auxiliary energy from battery AB to the rails as long as the reception of coded signal control energy at the section entrance is interrupted. Under the conditions stated, the impulse relay IR receives pick-up current over a circuit which extends from the positive terminal of auxiliary battery AB through conductor 32, back contact E9 of relay TR, conductors 4'! and 52, back contact 23 of relay IR, conductor 53, back contact 2% of relay DRlfa, conductor 33, the winding of relay IR and conductors M and 45 back to the negative terminal of battery AB.

Responding in a manner which will be characterized by the term bell action, the impulse relay IR recurrently picks up and releases at a speed which is determined by the period of its release delay and which has already been assumed to be of the order of about ten times per second. The bell action cycle begins when contacts 59 and 28 of relays TR'and DRlB become simultaneously released and continues as long as the named contacts occupy the released position.

Under that condition, each release of contact 23 of relay IR completes the relay pick-up circuit already traced above and causes battery AB to circulate through the relay winding a pulse of current which lifts contacts 2;] and 23 to the uppermost or picked up position. There the contacts remain until the expiration of the release delay period at which time they again drop out to once more complete the relay pick-up circuit. This causes the cycle just described to be repeated and thereby produces a pumping action 7 in the relay IR at intervals which are determined by the release time of that relay.

Each time that relay IR thus becomes picked up, contact 2i thereof connects the track rails l and 2 in energy receiving relation with the auxiliary battery AB over the circuit previously traced hereinbefore as including back contact [9 of relay TR and front contact 2i of relay IR. In this manner, the section rails are recurrently supplied with auxiliary energy from battery AB under the bell action control of relay IR as long as the code following track relay TR. fails to receive coded signal control energy from the rails.

As soon as the rear of the departing train clears the exit of the rear section D-Da, the rails of that section transmit the just described auxiliary energy forwardly to the winding of the detector rel y KR at the cut location Da and effect an immediate response of that relay to the clearing of the approach section. As long as any part of the train remains in the forward section DaE, the winding of relay KR remains continuously connected with the rails of the rear section due to the fact that contact 5 of the forward section relay TRa then continuously occupies its released or lowermost position. Accordingly, even though the rear section now is vacant no coded signal control energy is supplied to the rails thereof and the impulse relay IR at the entrance end continues to pick up and release in the recurrent bell action manner previously described.

Each pick-up of that relay causes the auxiliary battery AB to energize the detector relay KR over a circuit which may be traced from the positive terminal of the battery through conductor 42, back contact if: of relay TR, conductor 41, impedance 48, front contact 2i of relay IR, conductor 3'5, track rail 2, conductor 31, the winding of relay KR. conductor 49, back contact 5 of relay 'IRa, conductor 33, track rail l and conductor 34 and 45 back to the negative terminal of battery AB.

In responding to these recurring pulses of auxiliary energy, the detector relay KR at the cut location again causes the approach relay AR to receive recurring pulses of local energizing current. These are spaced sufficiently closely as to be bridged by the period of release delay of relay AR and in consequence that relay is by them maintained continuously picked up. This pick-up action interrupts at contact [3 the operating circuit for the highway crossing signal XS and thus restores that signal to its normally inactive state. At the same time, contact l5 disconnects the primary of transformer TT from its energizing source BC and thus discontinues the supply of alternating current energy to the rail supply circuit (still interrupted at contact 5 of device TRa).

When the rear of the departing train has cleared the exit end of the forward section DaE, the rails of that section once more transmit coded energy from the exit end of battery TB to the code following relay 'IRa at the cut location. That relay picks up its contact 5 in step with the received pulses of the named coded energy and thereby restores the supply of coded signal control energy from the cut location track battery TB to the rails of the rear section D-Da. These rails once more transmit the named energy to the track relay TR at the entrance location D.

That r lay once more responds and causes decoding relay DRi5 to pick up its contacts. Contact 23 now interrupts the local code producing circuit for the impulse relay IR and restores the control of the pick-up energy supply for that D in that figure.

relay to front contact IQ of the track relay Relay IR once more responds in the normal vacant track section manner and acts in conjunction with the code following relay TR to connect the track rails in energy receiving relation with the auxiliary battery AB during each off period of the received signal control code.

As in the case of the locally controlled pulses of this auxiliary energy, these off period pulses thereof are transmitted by the rails to the detector relay KR at the cut location Do. and the detector relay responds to them in normal vacant track section manner and thus continues to maintain the slow release approach relay AR in its normally picked up condition wherein it maintains the highway crossing signal XS inactive and the cut location transformer TT deenergized.

Further regarding my improved entrance end facilities which I have shown. at location D in Fig. 1, it has already been pointed out that the period of release delay for the impulse relay IR is so chosen that the connection of the auxiliary battery AB with the track rails is maintained for substantially the full duration of the shortest off period in all of the various codes to which the signaling system track relay TR is called upon to respond. From a further inspection of the circuits of Fig. 1, it will be seen that the auxiliary energy supply circuit is set up by contact 2! during each on period of the received signal control code and is completed by contact l9 the instant that the track relay TR releases at the beginning of the off period. This assures that the rails are supplied with the auxiliary or approach control energy from battery AB at the earliest possible time in each of the off periods.

The improved arrangement of Fig. 1 further insures that the auxiliary connection will be maintained for as large a portion of each 01f code period as is possible. Relay 11?. has its slowness of release so adjusted that it will drop out contact 2i only just before the already mentioned shortest off period has expired. This adjustment is capable of relatively accurate setting and it thus cooperates to insure that the maximum practical time of connection of the auxiliary battery with the rails will be realized. Once selected to meet the limiting conditions of the highest speed code of the signaling system, the relay IR provides the same fixed period of rail connection transfer for all other signaling system codes. That is, even with the lower speed or '75 pulse per minute code previously referred to the period of rail connection transfer will still be the same as for the 180 pulse per minute or high speed code despite the fact that the total length of the '75 code off period is of the order of 0.40 second as compared with about 0.15 second for the 180 code.

Referring to Fig. 2, I have there represented a somewhat modified form of entrance end facilities which are suitable for use with the track section clearing scheme of Fig. 1 and which may be substituted for the apparatus represented at These modified facilities of Fig. 2 are generally equivalent to the corresponding entrance end apparatus earlier described and in considering them it will be hel ful to assume that the conductors 3G and 36 of Fig. 2 are joined at location D with the track rails l and 2 of Fig. 1 which extend forwardly to location Da of the same figure where they are connected with the cut location facilities of which the detector and approach relays HR and AR form a part.

The modified facilities of Fig. 2 difier, however, from those of Fig. 1 in that the circuit over which the auxiliary battery AB supplies approach control energy to the track rails is simpliried and in that the impulse relay R2 is supplied with pick-up energy from the secondary winding of a transformer RT instead of from the battery AB.

This transformer RT is provided with a direct current primary energizing circuit which is pole changed by a contact of the code following track relay TR and which derives energy from a local source designated by the terminals plus and minus. Each ti -e that the track relay releases the pole changing action of this contact 55 causes to be induced in the secondary Winding of the transformer a pulse of voltage having the polarity designated by the small arrow, and which for convenience will be referred to as positive. Each time that the track relay is picked up, the action of the contact 55 causes to be induced in the same winding a pulse of transformer voltage of the opposite or negative polarity.

Both half-waves of voltage from the transformer RT are impressed upon the operating winding of the impulse relay IRE. As shown, this relay is of the polar type and contact 2i thereof occupies the lowermost position (shown in full lines) as long as the relay remains deenergized or receives current of the negative polarity just described. In that released position, the contact connects the operating winding of the track relay TR directly across the track rails and 2, as in the case of the apparatus of Fig. 1.

When, however, relay 1R2 receives from the transformer RT the before mentioned pulse of positive or normal polarity energy, it picks up its contacts and thereby disconnects relay TR from the track rails and connects the auxiliary battery AB thereacrcss by way of a relatively simple circuit which includes the current limiting impedance M. Due to the momentary character of the normal polarity output pulse of transformer RT, the duration of each of these connection shifts is comparatively short. For prolonging it to a value of the order already described in connection with the apparatus of Fig. 1, the relay 1R2 is preferably made slow releasing.

The just described transformer RT supplies pick-up current to the impulse relay IRZ only when the track relay TR is responding to coded signal control energy received over conductors 34 and 36 and is causing decoding transformer DT to supply decoding relay DR75 with energy which maintains that relay continuously picked up. Under that condition, the output winding of transformer RT is connected with the operating winding of relay IRE over a pair of front contacts 56 and El of relay DR'l5 and conductors 53 and 59.

When the track relay TR fails to respond to received coded energy, relay DRTS releases in the usual manner and contacts 5i; and 5'17 then transfer the connection of conductors 58 and 59 from the secondary of transformer RT to a source of direct current energization designated by the terminals plus and minus. Interposed between this source and the relay supply conductors 58 and 59 is a contact 23 of the impulse relay IRZ which completes the energizing connection only when the relay is released. As in the apparatus of Fig. 1, this contact 23 functions to cause the impulse relay 1R2 to pick up and release recurrently whenever the decoding relay DR'I5 is released.

The operation of a track section clearing system employing the modified entrance end facilities of Fig. 2 is basically the same as that already explained in connection with the earlier described complete system of Fig. As long as the track relay TR of Fig. 2 receives coded signal control energy from the rails of the approach section (see DDa of Fig. 1) the decoding relay DRl5 is picked up and the winding of the impulse relay IE2 is connected in energy receiving relation with the supply transformer RT. Under such conditions, each pulse of coded signal control energy received from the trackway picks up the track relay TR over a circuit which includes conductor the winding of relay TR, conductor 35,

back contact 2i of relay 1R2 and conductor 36.

At the end of each of these on code periods the track relay TR releases and the accompanying movement of contact thereof pole changes the direct current exciting circuit for the transformer RT in such manner as to induce in the secondary winding that transformer a pulse of normal polarity voltage which picks up the impulse relay IR2 over a circuit which may be traced from the upper terminal of the transformer secondary through front contact 56 of relay DR'i5, conductor 58, the winding of relay 1R2, conductor 59 and front contact 51 of relay DRl back to the lower terminal of the transformer secondary.

This energization of relay IRE occurs at the beginning of each of the off periods of the received signal control code. In responding, contact 2! of relay IR? momentarily picks up and disconnects the winding of relay TR from the track rails and connects the auxiliary battery AB thereacross. Under this condition, the battery picks up the detector relay KR (see the cut section location Da of Fig. 1) over a circuit which may be traced. from the positive terminal of battery AB through impedance 1%, front contact H of relay 1R2, conductor 33, the track rails and the winding of relay KR (not shown in Fig. 2 but see Fig. 1) and conductor back to the negative terminal of battery AB.

In this manner, the rails of the track section to which conductors tit and 36 are connected receive a pulse of auxiliary energy from the battery AB of Fig. 2 during each of the off periods of the signal control code which is received and responded to by relay TR. it the opposite or exit end of the approach section (see location Da of Fig. 1) the code following detector relay KR2 responds to this auxiliary energy and causes the approach relay AR to be supplied with corresponding pulses of local pickup current which maintain the contacts l3 and i i of that relay in the normally picked up position.

When a train comes into the section of track In consequence, relay 1R2 recurrently picks up and releases in the bell action manner already explained in connection with relay IR of Fig. 1. That is, each time that the relay is released it completes for its own winding an energizing circuit which may be traced from the positive supply terminal through back contact 23 of relay 1R2, conductor 6|, back contact 56 of relay DRZ5, conductor 58, the winding of relay IE2, conductor 59, back contact 51' of relay DRlB and conductor 62 back to the negative supply terminal.

This energization picks up the relay contacts and completes at 23 a snubbing circuit for the relay winding, which snubbing circuit may be traced from the right terminal of that winding through conductor 58, back contact 56 of relay D2115, conductor 6!, front contact 23, conductor 62, back contact 51 of relay DR15 and conductor 59 back to the left terminal of the relay winding. This snubbing tends to prolong the period of contact hold-up to a value which is commensurate with that which is produced by the vacant track section energization of the winding from the secondary of transformer RT.

At the expiration of that hold up period the relay contacts once more release and thus cause the cycle just described to be repeated, whereby the relay recurrently picks up and releases at some predetermined rate, such as ten times per second. In this manner contact 2! is caused recurrently to connect the auxiliary battery AB in energy supplying relation with the rails of the track section from which conductors 34 and 36 of Fig. 2 lead.

As soon as the rear of the departing train clears that section, the rails thereof transmit auxiliary energy from battery AB to the detector relay KR! (see Fig. 1) at the section exit and thus restore that relay to its normally active state. Later, when coded energy is again supplied from the rails of the approach section (see DDa of Fig. 1) to conductors 3i and 35 (this happens when the train moves out of the forward section DaE of Fig. 1), the track relay TR of Fig. 2 once more responds and picks up decoding relay DR'IS. Contacts 56 and 57 of that relay once more transfer the connection of the winding of the impulse relay 1R2 back to the transformer RT and from this point on the entrance end facilities of Fig. 2 operate in the normal or vacant track section manner already explained.

As compared with the corresponding entrance end facilities which are shown at location D in Fig. 1, the organization of apparatus which I have represented in Fig. 2 has the advantage of being immune to the false operating effects of steady energy which at times may accidentally or otherwise be supplied to the rails of the approach track section indicated at D-Da in Fig. 1. Such steady energy in the rear section would be encountered even in the system of Fig. 1 were the code repeating facilities shown at the cut location Da to be modified to the extent that each on period of the coded energy received from the forward section DaE would produce an off period in the similarly coded energy supplied to the rails of the rear section DDa.

As now represented, however, the on code periods are coincident in the two sections by virtue of the illustrated arrangement wherein contact 5 of the forward section relay 'IRa coinpletes the rail energizing circuit for the rear section when in its uppermost or front position. This may be referred to as front contact coding. The modified arrangement above referred to employs back contact coding and in that sittion. For such a condition, the entrance end apparatus of Fig. i would not operate in the manner intended for the reason. that the contacts of the track relay TR would be held continuously picked up instead of being allowed to remain shown at location D require for their intended operation.

The modified entrance end facilities of Fig. 2 are not subject to this limitation since in them the position of the track relay contacts does not affect the circuits by which auxiliary energy from battery AB is recurrently supplied to the track rails under the control of contact 2% of impulse relay 1R2. Even though the contacts 9, H and of the track relay TR are held continuously picked up, the decoding relay DR'IS will release in the same manner as when the track relay contacts are continuously released and having so done, the impulse relay IE? will repeatedly pick up and release under the control of bell action" contact 23 thereof. In this manner the facilities of Fig. 2 assure that the auxiliary battery A13 will recurrently be connected with the track rails when the contacts of the code following track relay TR. continuously occupy either the released 5'.

or the picked up position.

Referring now to Fig. 3, I have there represented a modified form of cut location facilities which may be used in place of the apparatus which is represented at location Dd in Fig. 1. This modified apparatus is generally equivalent to the corresponding facilities earlier described and in considering it, it will be helpful to assume that the track rails i and extending rearwardly from the location of the cut terminate in entrance end facilities of the character shown at location D in Fig. i (or as modified in accordance with Fig. 2) and that the rails extending forwardly from the cut location Dd terminate in coded energy supply facilities of the character respects: First in the interposition of a transformer AT between the operating winding of the slow release approach relay AR and its local direct current source of supply and second in the provision of a code following detector relay KR2 provided with a hold-up winding 64 which is separate from the pick-up winding 65 and which is energized under the control of an added relay KA.

The object of the interposed transformer AT is to insure that the approach relay AR will receive pick up energy only when the controlling detector relay KR? is following code and not when, as in the system of Fig. l, the detector relay may be caused, as by the reception of steady energy from the trackway, to hold its contact 25 continuously picked up. Instead of directly controlling the winding circuit for relay AR this contact 25 in Fig. 3 pole changes the direct current exciting circuit for the interposed transformer AT and the relay AR then receives released continuouslyas the circuits the output voltage of this transformer over a rectifying contact 66 which is .added to the detector relay (in accordance with the teachings of the before referred to copending application Serial No. 210,745 of Frank H. Nicholson et a1.) and operated in synchronism with the first contact 25.

As long as the detector relay KRZ maintains its contacts in either the released or the picked up position continuously, primary current from the. local source designated by the terminals plus and minus steadily flows in the same direction through a portion of the transformer primary. Under this condition there is no change of flux in the magnetic circuit of the transformer to induce an output voltage in the secondary winding so that relay AR remains deenergized. When, however, the contacts of the detector relay KRZ are recurrently moved between the picked up and the released positions, the direction of exciting current flow through the transformer primary is recurrently reversed and the secondary winding of the transformer AT then has induced therein a wave of alternating current voltage which is rectified by contact 66 of relay KRZ and caused to circulate through the operating winding of the slow release approach relay AR recurring pulses of unidirectional current which cause that relay to maintain its contacts l3 and i5 continuously picked up as long as the detector relay KR2 continues to follow code.

In this manner, the relay AR is rendered responsive only to the reception of recurring pulses of auxiliary energy from the entrance end battery AB (see Figs. 1 and 2) and is rendered immune to steady or continuous energy which may bereceived from that battery or any other source by the pick-up winding 65 of relay KR? over the rails of the rear section which has its exit at the cut location Do.

Considering now the second point of difference between the cut location equipments of Figs. 3 and 1, it, as has already been indicated, resides in the provision of a separate hold-up winding 64 on the code following detector relay KHZ and added facilities including a relay KA for supplying energizing current to this hold-up winding at proper times. The function of this winding 64 is to prolong the hold-up time of the code following detector relay KRZ to substantially the full duration of the signal control code 01f period' within which each pick-up response of the detector relay occurs.

This is desirable when the signaling system is operating at the lower pulse rate codes (such as the before described 75 pulse per minute rate) and then receiving at the exit end of the ap.

proach orrear section (see D Da of Fig. 1) pulses of auxiliary energy from the section entrance (see location D of Fig. 1 and see also Fig. 2) which have the same restricted duration as is determined by the highest pulse rate code (before assumed to be pulses per minute) which the signaling system employs.

This .code correction function tends to equalize the periods of contact pick-up and release for the detector relay KR2 at all code speeds and thus insures that the output of the interposed transformer AT will be substantially balanced in. character and will permit the period of release delay forthe approach relay AR to be reduced below that necessary were the output of transformer AT to have the relatively unbalanced character at low code speeds which would result were the contacts of the code following detector relay CR to remain picked up (as in the arrangement of Fig. 1) only for the 'duration of the comparatively short pulses of auxiliary energy received from the entrance end of the approach or rearwardly extending section.

Such a reduction in the releaseperiod for the relay AR, of course, quickens the response of the track section clearing apparatus to a shunting of the approach track circuit. By thus detecting the absence of received auxiliary energy within a shorter time, it is possible to avoid cab signal flips at block joints. This problem is discussed more fully in copending application Serial No 221,317, filed July 26, 1938, for Approach control apparatus for railway signaling systems by Edward U. Thomas and assigned to the Union Switch & Signal Company.

In operation of the code correction means which I have represented in Fig. 3, the pick-up winding 65 of the detector relay KRZ is connected in energy receiving relation with the rear section rails over the back point of coding contact 5 in the same manner as is the operating windingof the detector relay KR in Fig. 1. due to the action of this pick-up Winding, the relay KRZ of Fig. 3 responds to each received pulse of auxiliary energy in the usual manner and picks up contacts 25 and 66 at the beginning of each of such pulses.

Controlling the energizing circuit for the holdup winding 64 of relay KR2 is an added relay KA which is a slow releasing device and the operating Winding of which is supplied with energizing current from a local direct current source each time that an added contact 61 of the forward section code following relay TRa occupies the uppermost or on code period position. During the off code periods when this contact 61 is in the lowermost position, it'then interrupts the energizing circuit for relay KA (shown as including a conductor 68) and completes for the hold-up winding 64 of relay K32 an energizing circuit which may be traced from the positive terminal of a suitable supply source through back contact 6'! of relay TRa, conductor 69, a front contact 10' ,back contact 61 of relay 'IRa for the full duration of each 01f code period.

When the forward section relay TRa fails to receive coded energy and allows its contacts 5 and 61 continuously to occupy the lowermost position, relay KA is continuously deenergized and it then releases contact 10 and thus breaks the hold-up circuit for relay KRZ at that point. The condition just outlined obtains when the forward section which has its entrance at the cut location Do, is occupied by any portion of the train. 'Under that condition, only the pick-up winding 65 of relay KRZ is effective in controlling the relay and then the duration of its contact pick-up is determined solely by the length of the pulses of auxiliary energy which are received overv the Accordingly,

rear section rails from the battery AB (see Figs. 1 and 2) at the rear section entrance.

The manner in which the extended cut location facilities of Fig. 3 operate will have become more or less evident from the foregoing description. As long as the forward track section is vacant, relay TRa responds to coded signal control energy received over the forward section rails and repeats this energy into the rear section rails over front contact 5. When the rear section also is vacant, the code following track relay at the entrance end thereof (see Figs. 1 and 2) responds to this energy and holds the decoding relay DR15 picked up, thereby causing the impulse relay IR to connect the auxiliary battery AB in energy supplying relation with the rails during each off period of the received signal control code. At the exit end of the rear section the pick-up winding of the detector relay KRZ receives these recurring auxiliary pulses and picks up the contacts 25 and 66 at the beginning of each one of them.

Meanwhile, the added relay KA holds contact Ill continuously picked up by virtue of the energy received over front contact 6'! of relay 'IRa and this same contact 6'! causes the hold-up winding 64 of relay KR2 to be energized for the full duration of each of the off code periods. Regardless of the speed of the signal control code which is being repeated around the rail joints 3 at the cut location Da, the pick-up and release periods of the detector relay contacts are sub stantially equal and the interposed transformer AT supplies the slow release approach relay AR. with energy which holds contacts I3 and i5 continuously picked up, thereby maintaining the crossing signal XS inactive and keeping the primary of the track transformer 'IT deenergized.

If, now, a train comes into the rear or approach section (having its exit at location Da) the shunting action of its wheels and axles renders the section rails inefiective for transmitting energy in either direction and the entrance end track relay TR releases thereby causing decoding relay DR'I5 also to drop its contacts. Under this condition, the impulse relay 1R2 becomes effective locally to code energy which the auxiliary source AB supplies to the rear section rails. At the cut location Do, the pick-up winding 65 of detector relay KRZ is deprived of the recurring pulses of auxiliary energy and only the hold-up winding 64 of that relay is recurrently energized from the local source designated by the terminals plus and minus.

The design of this hold-up winding is such that while it is effective to maintain the contacts of relay KR2 in the picked up position once they have been there moved by the pick-up winding 65, yet it produces insufiicient magnetizing force to independently move the contacts from the originally released position without aid from the pick-up winding 65. Accordingly, relay KRZ remains continuously released under the conditions now being described and this causes the slow release approach relay AR also to release. Contact I3 now completes the operating circuit for the crossing warning signal XS and places that signal in operation while contact [5 connects the primary of the track transformer T1 with its alternating energizing current source 13-6 and thus causes the rails of the rear section to be supplied with coded alternating current energy which is suitable for the control of train carried cab signals.

As the forward end of the train passes over the cut location rail joints at Do, the forward section relay 'IRa becomes continuously deenergized and it then allows its contacts 5 and 57 continuously to occupy the lowermost position. Contact 5 now connects the pick-up winding 65 of relay KR2 continuously in energy receiving relation with the rear section rails while contact 6'! interrupts the energizing circuit for the added relay KA and causes that relay to release its contact 10, thereby breaking the energizing circuit at that point for the hold-up winding 64 of the detector relay KRZ.

When the rear of the train clears the cut location Do, the winding 65 of the detector relay KRZ receives from the rear section rails the before described recurring pulses of auxiliary energy which are supplied from the entrance end source AB under the control of the impulse relay IR (see Figs. 1 and 2). In responding to this energy, the contacts 25 and 55 of the detector relay recurrently move between the picked up and released positions, and the slow releasing approach relay accordingly receives current through transformer AT which holds its contacts continuously in the picked up position. Contact l3 now interrupts the energizing circuit for the crossing signal XS and discontinues operation of that signal, while contact I5 disconnects the primary of transformer TI from the alternating energizing source B-C.

As the rear of the departing train clears the exit end of the forward section (see location E of Fig. 1) the rails of that forward section again transmit coded signal control energy to the cut location relay TRa, that relay resumes code following operation and repeats the coded energy pulses into the rear section rails, those rails transmit the repeated energy to the entrance end track relay TR (see location D of Fig. l and also see Fig. 2), that relay picks up the decoding relay DR'IS, the associated impulse relay IR now responds to connect the rear section rails in energy receiving relation with the auxiliary source AB, those rails transmit the auxiliary energy forwardly to the pick-up winding 65 of the detector relay KRZ at the cut location Da, and that relay resumes code following operation in the normal vacant track section manner, thereby continuing to hold the slow release approach relay AR continuously picked up. Meanwhile, the added relay KA once more becomes picked up to enable the hold-up winding 64 of the detector relay to be recurrently energized over back contact 6'! for the purpose of effecting the before described code correction.

From the foregoing, it will be seen that I have made important improvements in track section clearing apparatus which is suitable for use with systems of railway signaling wherein coded track circuit energy is employed to control wayside and/or cab signals. In particular, I have eliminated the need for line wires between the entrance and the exit end of the section of track which is to the rear of the cut location; I have minimized the danger of improper operation of the clearing apparatus due to an accidental failure of the signaling system track relay to respond to coded track circuit energy; I have safeguarded the clearing apparatus against false response to foreign energy in the track circuit; I have quickened the response of the apparatus to a shunting of the approach section of track; and I have accomplished all of the above through the use of circuits of comparatively simple character.

While I have explained my invention in an application wherein both the operation of a highway crossing warning signal and the supply of alternating current cab signal energy are approach controlled, it will be understood that either one of these functions may be performed separately and that other comparable track section clearing functions, such as the operation of detector locking track circuits, may also be provided for in my new system.

Although I have herein shown and described only a few forms of track section clearing apparatus embodying my invention, it is understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

1. In combination with a section of railway track, means at the exit end of said section for at times supplying the rails thereof with recurring pulses of coded signal control energy and for at other times discontinuing said supply, means located at the entrance end of said section and controlled by the said pulses of coded energy which at times are there received for supplying auxiliary energy to said rails during the periods which separate the said received pulses of that coded energy, means also at said section entrance which become effective when no coded energy is there received from the section rails for then continuing to supply said auxiliary energy to those rails, and trafiic governing apparatus at the exit end of said section controlled by saidauxiliary energy and rendered inactive as long as that energy is transmitted over said rails to said section exit.

2. In combination with a section of railway track, means at the exit end of said section for at times supplying the rails thereof with recurring pulses of coded signal control energy and for at other times discontinuing said supply, a code following track relay at the entrance end of said section connected with said rails and operated by the said coded energy which is received therefrom, -a decoding relay controlled by said track relay and arranged to pick up when the track relay follows code, a source of auxiliary energy at said section entrance, means controlled by said track relay and rendered active when said decoding relay is picked up for connecting said source in energy supplying relation with said rails during the periods which separate the said received pulses of coded energy, means rendered active when said decoding relay is released for then also connecting said source in energy supplying relation with said rails, and traffic governing apparatus at the exit end of said section controlled by energy received over said rails from said auxiliary source and rendered inactive as long'as that energy continues to be received at said section exit.

3. In combination with a section of railway track, means at the exit end of said section for at times supplying the rails thereof with coded track circuit energy and for at other times'discontinuing said coded energy supply, a relay at said section exit having a slowness of release which is sufiicient to bridge the intervals be- .tween consecutive off periods of said track cirtion; a code following track relay connected with said rails at said section entrance end and operated by the said coded track circuit energy which is there received, a circuit controlled by said track relay over which said entrance end source supplies auxiliary energy to said rails during the said off periods of the said coded track circuit energy which at times is received by the track relay and also when no coded energy is received by that relay, and means at the said section exit for energizing said slow release relay in step with the pulses of said auxiliary energy which are there received from the section rails whereby to maintain that relay picked up as long as said section remains vacant.

4. In combination with adjoining forward and rear sections of railway track, means for supplying recurring pulses of coded energy to the rails of said forward section, a code following relay at the entrance end of said forward section connected to receive said coded energy from said forward section rails, means located at the exit end of said rear section and including a front contact of said code following relay for supplying the rails of said rear section with recurring pulses of coded energy which are in step with the forward section pulses to which the code following relay responds whereby to control trafiic which enters the rear section, means at the entrance end of said rear section for supply ing the rails thereof with auxiliary energy during the periods which separate the said pulses of coded rear section energy there received and also when no coded energy is there received, traffic governing apparatus at the exit end of said rear section including a control relay which is responsive to said auxiliary energy, and means including a back contact of said forward section code following relay for connecting the operating winding of said control relay in energy receiving relation with said rear section rails continuously under occupied conditions of said forward section and also during each interval which separates the said pulses of coded rear section energy which are supplied to those rails under vacant conditions of the forward section.

5. In combination with a stretch of railway track which is intersected by a highway, means for defining in said track a track circuit section which extends away from said intersection in the trafiic opposing direction, a crossing signal for warning the users of said highway of the approach of railway traffic over said section, means at the exit end of said section for supplying coded track circuit energy to the rails of said section at times and for discontinuing said coded energy supply at other times, a relay at said section exit having a slowness of release which is sufiicient to bridge the intervals between consecutive off periods of said track circuit code, means governed by said relay for supplying operating current to said crossing signal when and only when that relay is released, a source of auxiliary energy at the entrance end of said section, a code following track relay connected with said rails at said section entrance end and operated by the said coded track circuit energy which is there rereceived from the section rails whereby to maintain that relay picked up as long as said section remains vacant.

6. In combination with adjoining forward and rear sections of railway track, means for supplying recurring pulses of coded energy to the rails of said forward section, means controlled by the said pulses of coded energy which are received at the entrance end of said forward section for repeating similarly recurring pulses of coded energy into the rails of said rear section whereby to control traffic which enters that rear section, means at the entrance end of said rear section effective when said repeated pulses of coded tramc controlling energy both are and are not there received for supplying the rear section rails with pulses of auxiliary energy that spacedly recur under all conditions of their supply and that during said entrance end reception of said trafiic controlling pulses coincide with the recurring periods by which those received pulses are separated, and traffic governing apparatus at the exit end of said rear section controlled by the said auxiliary energy and rendered inactive as long as that energy is transmitted over the rear section rails to said rear section exit.

'7. In combination with adjoining forward and rear sections of railway track, means for supplying recurring pulses of coded energy to the rails of said forward section, means including a coding device controlled by the said recurring energy pulses which are received at the entrance end of said forward section for repeating similarly recurring pulses of coded energy into the rails of said rear section whereby to control traffic which enters that section, means at the entrance end of said rear section for supplying the rails thereof with auxiliary energy during the periods which separate the said pulses of coded energy which are there received and also in recurring pulse form when no coded energy is there received, traiiic governing means at the exit end of said rear section including a relay which is responsive to said auxiliary energy, and means controlled by said coding device for connecting the operating winding of said relay in energ receiving relation with said rear section rails continuously under occupied conditions of said forward section and also during each interval which separates the said pulses of coded rear section energy which are supplied to those rails under vacant conditions of the forward section.

8. In combination with adjoining forward and rear sections of railway track, means for supplying recurring pulses of coded energy to the rails of said forward section, means controlled by the said energy pulses which are received at the entrance end of said forward section for supplying similarly recurring pulses of coded energy to the rails of said rear section whereby to control traffic which enters that section, means located at the entrance end of said rear section and controlled by the said pulses of rear section energy which there received for supplying auxiliary energy to said rear section rails during the periods which separate the said received pulses of coded energy, means also at said rear section entrance which become effective when no coded energy is there received from the rear section rails for then continuing to supply those rails with recurring pulses of said auxiliary energy, and traffic governing apparatus at the exit end of said rear section controlled by the said auxiliary energy and rendered inactive as long as that energy is transmitted over the rear section rails to said rear section exit.

9. In combination with adjoining forward and rear sections of railway track, means for supplying recurring pulses of coded energy to the rails of said forward section, means controlled by the said pulses of coded energy which are received at the entrance end of said forward section for repeating similarly recurring pulses of coded energy into the rails of said rear section whereby to control traffic which enters that rear section, means at the entrance end of said rear section effective when said repeated pulses of coded traflic controlling energy both are and are not there received for supplying the rear section rails with pulses of auxiliary energy that spacedly recur under all conditions of their supply and that during said entrance end reception of said traffic controlling pulses coincide with the recurring periods by which those received pulses are separated, an approach relay at the exit end of said rear section having a slowness of release which is sufiicient to span the spacing between the said recurring pulses of said entrance end supplied auxiliary energy, means also at said rear section exit for energizing said approach relay in step with the pulses of said auxiliary energy which are there received from said rear section rails whereby to maintain that approach relay picked up as long as said rear section remains vacant, and traffic controlling apparatus governed by said approach relay and rendered active when that relay releases in response to the entry of a train into said rear section.

10. In combination with a section of railway track, means at the exit end of said section for at times supplying the rails thereof with recurring pulses of coded signal control energy and for at times discontinuing said supply, a code following track relay at the entrance end of said section connected with said rails and operated by the said coded energy which is received therefrom, a decoding relay controlled by said track relay and arranged to pick up when the track relay is following code and to release when the track relay is inactive, a source of auxiliary energy at said section entrance, means rendered effective when said decoding relay is picked up for connecting said source in energy supplying relation with said rails during the off periods of the said received coded energy and rendered effective when said decoding relay is released for then also intermittently connecting said source in energy supplying relation with said rails, and trafiic governing apparatus at the exit end of said section controlled by energy received from said auxiliary source and rendered inactive as long as that energy is transmitted over the rails to said section exit.

11. In combination with a section of railway track, means for supplying recurring pulses of coded signal control energy to the rails of said section, a code following track relay at the entrance end of said section connected with said rails and operated by the said coded energy which is received therefrom, a source of auxiliary energy at said section entrance, an impulse relay controlled by said track relay and functioning to transfer said track rail connection from the operating winding of the track relay to said auxiliary energy source during each off period of the received signal control code and to return that connection to the track relay winding before the beginning of the next on period of that code, means responsive to a continuously released condition of said track relay for causing said impulse relay then also recurrently to connect said track rails in energy receiving relation with said auxiliary source, and trafiic governing apparatus at the exit end of said section controlled by energy received over said rails from said auxiliary source and rendered inactive as long as those rails continue to transmit that energy to said section exit.

12. In combination with a section of railway track, means for supplying the rails of said se tion with recurring pulses of coded signal control energy, a code following track relay at the en trance end of said section connected with said rails and operated by the said coded energy which is received therefrom, asource of auxiliary energy at said section entrance, a slow release impulse relay effective when picked up to transfer said track rail connection from the winding of said track relay to said auxiliary source and effective when released to return that connection to the track relay winding, means for completing a bypass path from said rails to said winding each time that the track relay picks up, a decoding relay controlled by said track relay and arranged to pick up when the track relay is following code and to release when the track relay is inactive, an energizing circuit for said impulse relay which under picked-up conditions of said decoding relay is completed upon each pick-up of said track relay and under released conditions of the decoding relay is completed upon each release of said impulse relay, and trailic governing apparatus at the exit end of said section controlled by energy received over said rails from said amiliary source and rendered inactive as long as those rails continue to transmit that energy to said section exit.

13. In combination with a section of railway track, means for supplying the rails of said section with recurring pulses of coded signal control energy, a code following track relay at the entrance end of said section connected with said rails and operated by the said coded energy which is received therefrom, a source of auxiliary energy at the said section entrance, an impulse relay effective when picked up to transfer said track rail connection from the winding of said track relay to said auxiliary source nd effective when released to return that connection to the track relay winding, a decoding relay controlled by said track relay and arranged to pick up when the track relay is following code and to release when the track relay is inactive, means efiective under picked-up conditions of said decoding relay for supplying a pulse of pick-up current to said impulse relay at the beginning of each off period of the received signal control code, means effective under released conditions of said decoding relay for supplying said impulse relay with a pulse of pick-up current each time that the impulse relay releases, and traffic governing apparatus at the exit end of said section controlled by energy received over said rails from said auxiliary source and rendered inactive as long as those rails continue to transmit that energy to said section exit.

14. In combination with a section of railway track, means at the exit end of said section for at times supplying the rails thereof with recurring pulses of coded signal control energy and for at other times discontinuing said supply, means at the entrance end of said rear section effective when said repeated pulses of coded signal control energy both are and are not there received for supplying the rear section rails with pulses of auxiliary energy that spacedly recur under all conditions of their supply and that during said entrance end reception of said signal control pulses coincide with the recurring periods by which those received pulses are separated, a code following detector relay at the said section exit receiving said auxiliary energy from said rails as long as said section remains vacant but not receiving said coded signal control energy at any time, a relay having a slowness of release which is suflicient to span the intervals between the recurring responses of said detector relay which said received pulses of auxiliary energy produce, means including a transformer provided with an exciting circuit which is controlled by said detector relay for supplying energizing current to said slow release relay when and only when the detector relay is following code, and traiiic governing apparatus controlled by said slow release relay and rendered active when that relay is released.

15. In combination with a section of railway track, means at the exit end of said section for at times supplying the rails thereof with recurring pulses of coded signal control energy and for at other times discontinuing said supply, means at the entrance end of said section effective when said repeated pulses of coded signal control energy both are and are not there received for supplying the rear section rails with pulses of auxiliary energy that spacedly recur under all conditions of their supply and that during said entrance end reception of said signal control pulses coincide with the recurring periods by which those received pulses are separated, a code following detector relay at the said section exit provided with a pick-up circuit and with a hold-up circuit, means for transmittingthe said auxiliary energy which is received at the section exit to said pick-up circuit and for excluding said coded signal control energy therefrom whereby the detector relay responds to each of said received pulses of auxiliary energyand becomes inactive when said track section is occupied, means for completing said hold-up circuit from the time of each response of the detector relay until the end of the off code period within which that response occurs, traffic governing apparatus including a slow release control relay also at said section exit, and means for energizing said control relay in step with the responses of said detector relay whereby to maintain that relay picked up only as long as said track section remains vacant.

HERMAN G. BLOSSER. 

